I under stand OPi-GPIO is a drop-in replacement library for RPi.GPIO for the Orange Pi Zero. It added a new GPIO pin definition GPIO.SUNXI. However, I cannot find its definition. Can somebody let me know or point me to a link where it is defined? Thanks.

@martinayottee I tried network-manager. It appears working for some of the dongles and not the others. I will to do more testing.
Raspberry Pi works but I am not sure how do they handle it and it looks strange. In the interfaces file, the iface states are manual, not static or hdcp. If one need to change them to static, it has to be done in /etc/dhcpcd.conf file rather than in interfaces file. Do you have any idea what are they doing?

@rodolfo, @martinayottee:
Thank you both for your reply. I don't really need both to connect at the same time but try to have the option open. For example, normally, I will use ethernet. However, I might want to connect through wifi when move to another area with no ethernet connection.
I have tried network-manager but it does not work too well either. I can try once more. However, Raspberry Pi seems being able to do what I wanted. I hope Orange Pi PC can do the same thing too.

I have setup my OPi one according to @rodolfo's instructions but with both eth0 and wlan0 on the same subnet. If I plug in both ethernet cable and wifi dongle in, I can connect through either one by ssh, but if I pull out the ethernet cable, I cannot connect through the wifi address any more. If I only plug in ethernet cable, I can connect through its ip address. However, if I only plug in the wifi dongle, I can see both addresses but ssh to either address has no connection. Is there anyway to fix that?

@rodolfo
In your link, you are using two different subnet, i.e., ...2.x and ...3.x for eth0 and wlan0. What I want to do is to have both on the same subnet. They don't have to work at the same time but if I have the RJ45 connected, I want to use the ethernet. On the other hand, if the dongle plugged in but not the RJ45, I want it connected through wlan0. Will your setup work?
@martinayotte For what I wanted to do as stated above, will your setup work? If it does, what is your setup procedure?

I have tried a few different suggestions that I have seen online to implement wifi on Orange PC with a wifi dongle. However, none them can work reliably. OrangePi zero works but wifi speed is very slow (about 1-2Mbps). I recently tried using Raspberry Pi with wifi dongles. It is almost plug and play and very reliable. I hope there is a way to do the same on OPi. If anybody know one, please let me know. I will be happy to try it out and report back.